Cotton gins are used to separate cotton fiber from the seed and waste. Monitoring the properties of the cotton fiber passing through a gin to assure that the gin is functioning properly is important to obtaining a quality product. Historically, cotton has been classed according to, among other things, its color, leaf content, preparation, trash content, fiber length, micronaire and fiber strength. Originally, the classification of cotton relied upon the senses of human classers who would visually observe the cotton and assign it a grade accordingly. However, the use of human classers tends to be unreliable and heavily dependent upon the skill of the individual. In modern times, most cotton quality determinations are typically made by high-volume instruments. In order to monitor the desired properties of the cotton fiber, many conventional machines use an incandescent light bulb to illuminate the cotton as it rests upon a sample window from which it can viewed. The light that is reflected off of the cotton sample is then received by a photo sensitive detector. By examining the intensity of different wavelengths of light reflected by the sample, readings representing the quality and class of the cotton can be obtained.
Several disadvantages result from the use of an incandescent bulb to illuminate the cotton sample. Because the bulb is left on continuously when the gin is running, the intensity of the light produced by the bulb decays over time. Furthermore, in order to emit a white light of the desirable color temperature, an incandescent bulb must run at a high current. Continuous use of an incandescent bulb at a high current results in a dramatically reduced useful bulb life. Additional problems result from the vibration associated with cotton processing machinery. Like the degradation of the bulb over time, these vibrations affect the intensity of the light produced by the incandescent bulb, causing it to flicker. Thus, the intensity of the light reflected from the cotton sample tends to vary without variation in the quality of the cotton being observed. These vibrations also have a tendency to break the filament of the incandescent bulb. The net effect of using an incandescent bulb, that produces light of varying intensities, is that the sensors of the monitoring device must constantly be recalibrated and the incandescent bulb must frequently be replaced.
Another problem with traditional sensing methods is that, because of the relatively slow imaging speed of the photo sensitive detector, the speed of the cotton fiber passing in front of the constantly illuminated sample window tends to blur the image received by the photo sensitive detector. This tends to create an averaged, rather than an instantaneous reading. In order to receive a clear reflection for an instantaneous reading, the fiber moving through the processing machine must be stopped when the measurement is taken or a sample of fiber must be removed from the stream of fiber and placed upon the sample window.
What is needed, therefore, is a method and apparatus for measuring fiber properties that overcomes the problems of unreliability and inconsistency attendant with present fiber monitoring devices.